One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,8)(5,6)(11,15)(14,16)(25,26,30,31)(27,29,33,39)(28,35,37,32)(34,36,40,38)(1,3,6,4)(2,7,5,8)(10,13)(14,16)(17,18,21,20)(19,23,24,22)(26,31)(27,33)(32,35)(34,40)(1,2,6,5)(3,7,4,8)(9,10,12,13)(11,14,15,16)(17,19,21,24)(18,22,20,23)(25,27)(26,29)(28,34)(30,33)(31,39)(32,38)(35,36)(37,40)(1,4,6,3)(2,7,5,8)(9,11,12,15)(10,14,13,16)(17,20,21,18)(19,23,24,22)(25,28,30,37)(26,32,31,35)(27,34,33,40)(29,38,39,36)(1,5,6,2)(3,7,4,8)(25,29)(26,33)(27,31)(28,36)(30,39)(32,34)(35,40)(37,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.